A winter storm is an event in which the
dominant varieties of precipitation are forms
that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground
temperatures are cold enough to allow ice to form (i.e. freezing rain). In temperate continental
climates, these storms are
not necessarily restricted to the winter season, but may occur in
the late autumn and early spring as well. Very rarely, they may
form in summer, though it would have to be an abnormally cold
summer, such as the summer of 1816 in the Northeast United States of
America. In many locations in the Northern
Hemisphere, the most powerful winter storms usually occur in
March and, in regions where temperatures are cold enough,
April.

Snow

Wintry showers or wintry
mixes

Many factors influence the form precipitation will take,
and atmospheric temperatures are influential as well as ground
conditions. Sometimes, near the rain/snow interface a region of sleet
or freezing rain
will occur. It is difficult to predict what form this precipitation
will take, and it may alternate between rain and snow.
Therefore, weather forecasters just predict a "wintry mix".
Usually, this type of precipitation occurs at temperatures between
-2 °C and 2 °C (28 °F and 36 °F).

Heavy showers of freezing rain are one of the most
dangerous types of winter storm. They typically occur when a layer
of warm air hovers over a region, but the ambient temperature is
near 0 °C (32 °F), and the ground temperature is
sub-freezing. A storm in which only roads freeze is called a
freezing rain storm; one resulting in widespread
icing of plants and infrastructure is called ice
storm.

While a 10 cm (4 in) snowstorm is somewhat manageable by
the standards of the northern United States and Canada, a comparable 1 cm (0.4 in) ice
storm will paralyze a region: driving becomes extremely hazardous,
telephone and power lines are damaged, and crops may be ruined.
Because they do not require extreme cold, ice storms often occur in
warm temperature climates (such as the southern United States) and
cooler ones. Ice storms in Florida will often destroy entire orange crops.

The Ice Storm of December 2002 in North Carolina resulted in massive power
loss throughout much of the state, and property damage due to
falling trees. Except in the mountainous western part of the state,
heavy snow and icy conditions are rare in North Carolina.

The Ice Storm of
December 2005 was another severe winter storm producing
extensive ice damage across a large portion of the Southern United
States on December 14 to 16. It led to power outages and at least 7
deaths.

In January 2005 Kansas had
been declared a major disaster zone by President George W. Bush
after an ice storm caused nearly $39 million in damages to 32
counties. Federal funds were provided to the counties during
January 4–6, 2005 to aid the recovery process.[1]

The January
2009 Central Plains and Midwest ice storm was a crippling and
historic ice storm. Most places struck by the storm, saw 2 inches
or more of ice accumulation, and a few of inches of snow on top it.
This brought down power lines, causing some people to go without
power for a few days, to a few weeks. In some cases, some didn't
see power for a month or more. At the height of the storm, more
than 2 million people were without power.

Graupel

Ice crystals fall through a cloud of super-cooled
droplets-minute cloud droplets that have fallen below freezing
tempature but have not frozen. The ice crystal plows into the
super-cooled droplets and they immediately freeze to it. This
process forms graupel, or snow pellets, as the droplet
continues to accumulate on the crystal. The pellets bounce when
they hit the ground.

Ice
pellets

it is easily seen and does not accumulate ice, it is not as
dangerous as freezing rain.

Rime

Rime is a milky white accumulation of super-cooled
cloud or fog droplets that freeze when they strike an object that
has a temperature of 32 degrees F, 0 degrees C, or freezing. The
process is called riming when super-cooled cloud droplets
attach to ice crystals in the formation of graupel (see earlier
section if you have not already for more info on graupel). Rime ice
can pose a hazard to an airliner when it forms on a wing as an
aircraft flies through a cloud of super-cooled droplets.

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See also

Winter storms or snowstorms happen when warm, wet air meets with cold air. The warm, wet air mass and the cold air mass can each be 1000 km or more in diameter. Snowstorms affecting Northeastern United States often get their moisture from air moving north from the Gulf of Mexico and cold air from air masses coming down from the Arctic. In the Northwest United States warm, wet air from the Pacific Ocean cools when it is pushed upward by the mountains. Many different things can affect the direction of movement, moisture content and temperature of air masses. All of these differences affect the type and severity of the snowstorm.

Winter storms and blizzards can make several feet of snow that blow into big drifts. Sometimes the drifts can be over ten feet tall. They could even cover a house.

History

Lots of popular winter storms are part of North America's history. In 1846 the Donner Party traveled away by covered wagons from Illinois headed for Sutter's Fort near Sacramento, California. As a answer of bad decisions and slow going, they tried to go across the big Sierra Nevada Mountains in the late October. Usually, California is still warm at that time of the year. As the party crossed the Sierra Nevada Mountains, they did not see any snow and was not worried.
However, after they left, a huge snowstorm hit. The party was forced to camp near Truckee, California. The snow was so deep that the wagon wheels became stuck, so they could not move anyplace. They tried to wait the storm out, but when one blizzard ended, another began immediately before they had time to escape.
Their food became short, so some of the people decided to hike out and find help rather than to starve to death. Most of them died in the freezing weather, and many of those who stayed behind in the camp survived. Of the 87 people who started in Illinois, only 47 lived. [1]